If your answer is, “because I need a job,” dig deeper. Is there something special about the work the company does that gets you excited? Do their ambitions align with yours? Does the position feel like a great learning opportunity? Will your work have an impact on the world?
Look at the position from different angles. What about it strokes your passion? If, after careful consideration, “because I need a job” is still the best answer you can give, you might consider waiting for a company that gives you a reason to want to come to work.